Messages in this thread | | | Date | Tue, 5 May 2020 02:03:52 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf evsel: Get group fd from CPU0 for system wide event |
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On Sat, May 02, 2020 at 10:33:59AM +0800, Jin, Yao wrote:
SNIP
> > > @@ -1461,6 +1461,9 @@ static int get_group_fd(struct evsel *evsel, int cpu, int thread) > > > BUG_ON(!leader->core.fd); > > > fd = FD(leader, cpu, thread); > > > + if (fd == -1 && leader->core.system_wide) > > > > fd does not need to be -1 in here.. in my setup cstate_pkg/c2-residency/ > > has cpumask 0, so other cpus never get open and are 0, and the whole thing > > ends up with: > > > > sys_perf_event_open: pid -1 cpu 1 group_fd 0 flags 0 > > sys_perf_event_open failed, error -9 > > > > I actualy thought we put -1 to fd array but couldn't find it.. perhaps we should od that > > > > > > I have tested on two platforms. On KBL desktop fd is 0 for this case, but on > oncascadelakex server, fd is -1, so the BUG_ON(fd == -1) is triggered. > > > > + fd = FD(leader, 0, thread); > > > + > > > > so how do we group following events? > > > > cstate_pkg/c2-residency/ - cpumask 0 > > msr/tsc/ - all cpus > > > > Not sure if it's enough to only use cpumask 0 because > cstate_pkg/c2-residency/ should be per-socket. > > > cpu 0 is fine.. the rest I have no idea ;-) > > > > Perhaps we directly remove the BUG_ON(fd == -1) assertion?
I think we need to make clear how to deal with grouping over events that comes for different cpus
so how do we group following events?
cstate_pkg/c2-residency/ - cpumask 0 msr/tsc/ - all cpus
what's the reason/expected output of groups with above events? seems to make sense only if we limit msr/tsc/ to cpumask 0 as well
jirka
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